Deconstruction of oriented crystalline cellulose by novel levulinic acid based deep eutectic solvents pretreatment for improved enzymatic accessibility.

Discovering green solvents and their inner mechanisms for efficient deconstruction of lignocellulosic biomass recalcitrance are receiving growing interests. In this work, eco-friendly levulinic acid (LA) based deep eutectic solvents (DES) were proposed for pretreatment on moso bamboo by combining acetamide (Am), betaine (Ba) and choline chloride (ChCl) as hydrogen bonding acceptors. LA/ChCl pretreated materials showed optimal enzymatic accessibility with the highest glucose yield (79.07%) because of its higher lignin removal, morphological disruption and decreased crystallinity. Moreover, the microvoids (averagely 30 nm) and cracks were observed for cellulose microfibrils in anisotropic directions, which resulted in shorter microfibrils and crystallites facilitating the enzymatic hydrolysis. The studies on recyclability revealed that LA/Ba DES had better recycling performance due to its maintaining capability of lignin extraction. Series of supramolecular changes on oriented crystalline cellulose were determined in this work by novel LA based DES, which may provide new alternatives for biomass pretreatments.